In the past, engine coolant heat exchangers, such as radiators, have been made by providing a plurality of parallel, spaced-apart flat tubes with cooling fins located therebetween to form a core. Opposed ends of the tubes pass through openings formed in manifolds or headers located on each side of the core at the respective ends of the tubes. A difficulty with this type of construction is that the tube to header joints are difficult to fabricate and prone to leakage. As well, there is a tendency for the tube to header joints to fail as a result of stresses caused by thermal cycling. Therefore, this type of construction presents problems with both the manufacture and operation of the heat exchanger.
A method of overcoming these difficulties is shown in U.S. Pat. No. 3,265,126 which issued to D. M. Donaldson. In this patent, manifolds are provided with a continuous longitudinal opening, and the tubes are formed with specifically shaped ends to fit into this continuous opening, thus simplifying the assembly and reducing the leakage problem. A difficulty with the Donaldson structure, however, is that the shape of the various components is quite complex resulting in high tooling costs.
In order to facilitate the design of heat exchanger components and thereby reduce manufacturing costs, various improvements to headerless heat exchangers have been made. For instance, U.S. Pat. No. 6,332,495 which issued to Jamison et al. discloses a clip-on manifold heat exchanger formed from a plurality of stacked plate pairs having raised peripheral edge portions to define flow channels inside the plate pairs. The plates of the plate pairs are formed with offset, diverging end flanges that space the plate pairs apart. A U-shaped channel envelopes the plate end flanges to form part of a manifold at each end of the plate pairs, and end caps or plates close the open ends of the U-shaped channels to complete the manifolds. The components are typically joined together by brazing or any other suitable technique.
U.S. Pat. No. 6,513,585 which issued to Brost et al. discloses a headerless vehicle radiator formed of tubes having end walls which are bifurcated for a short distance from the ends of the tubes and having one or both of the sidewalls in the bifurcated segment of the tube formed outwardly and adapted to contact and be joined in a fluid tight manner with the sidewall of an adjacent tube in the radiator core. A collecting tank (or manifold) has walls extending partially over the radiator core to a distance beyond the bifurcation of the sidewalls, the collecting tank walls being joined to the end walls of the tubes in a fluid tight manner. Once again, the various components of the heat exchanger (or radiator) are typically joined together by brazing or any other suitable technique.
In both the Jamison et al. and Brost et al. heat exchangers, the performance of the heat exchanger depends in part on the effectiveness of the joint achieved between the plate pairs and the walls of the U-shaped channels or manifolds. Due to the thicknesses of the materials used in creating the components of these types of heat exchangers, it can be difficult to achieve an effective seal or bond between the plate pairs.